Treating big-end-down ingots



Patented Mar. 27, 1951 TREATING BIG-END-DOWN moors Edgar Marburg, Pittsburgh, Pa., assignor to United States Steel Company, a corporation of New Jersey Application February 13, 1948, Serial No. 8,171

4 Claims.

1 This invention relates to a method of treating big-end -down ingots and is a continuation-inpart of my copending application, Serial No. 602,912, filed July 2, 1945, now abandoned.

v, In preparing steel for rolling, hot metal is poured into an ingot mold having a hot top for providing a sinkhead which will not complete freezing until the remainder of the ingot has frozen. After the metal has become sumciently solidified, the mold is removed therefrom and the ingot is charged into the soaking p t. An ingot of normal size (18 to 25 inches per side) will freeze completely solid in 1 to 2 hours time if left in the mold. If exposed to air by stripping, the time will be somewhat less. In order to accomplish its purpose of providing a reservoir of liquid metal to prevent central pipe, the hot top sinkhead must be the last metal to freeze. If the ingot were allowed to freeze completely solid in the mold there would be no question about the sinkhead being the last metal allowed to freeze. However, it is uneconomical to hold all the ingots in their molds until completely solid and, therefore, they'are normally removed from the mold while their c nters are still liquid. The conventional hot tops now in use are removed from the ingot during or before stripping after which the liquid metal in the sinkhead, due to the smaller size of the latter and the thinner solidified wall formed therein will freeze at a faster rate than the ingot body. If the hot top is removed too soon after pouring, the sinkhead may then freeze before the ingot itself, andwhen the ingot finally freezes, a central cavity (secondary pipe) will develop due to the lack of feeder metal. It is necessary, therefore, to set a minimum time for ingots to be held at the platform so that when they are stripped, the freezing of the ingot body will be completed before that of the sinkhead. 'After the molds are stripped from the ingots and the latter are substantially solidified, they are charged into the soaking pits. Fire clay is the material commonly used to make hot tops and this material tends to fuse with hot metal, with the result that under the best conditions of stripping,. fairly large portions of the hot top may remainjjadhering to the ingot when it is heated in the soakingpitsand subsequently rolled. This clay may, and frequently does, cause damage to the surface of the rolls or ingots during rolling.

If it becomes mixed with the mill scale, it comprises a very undesirable component of the scale,

whichis recovered and charged into the blast ,furnace.

,.: The patent to Ken'ney, No. 1, 137, 1a4, discloses Ia-hot top which is retained on the ingot after stripping, but it also remains on the ingot in the It is an object of my invention to provide a method of treating big-end-down ingots in which the mold is stripped as soon as practicable from the ingot, but the hot top is retained in place until the ingot has substantially solidified and then removed prior to charging the ingot into the soaking pit.

A further object is to provide a method of treating big-end-down ingots which will increase the life of the ingot mold by reducing the length of time ingots must be held at the pouring platform before stripping. A still further object is to provide a method of treating big-end-down ingots whereby the time between pouring and charging is decreased, thus charging ingots at a higher temperature, shortening heating times, reducing fuel costs, and improving the quality of product by reducing scaling of ingot surfaces.

Another object is to provide such a method that can be carried out without the use of special equipment.

. These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

Figure l is a top plan view of the hot top in place on a mold;

Figure 2 is a sectional view on the line IIII of Figure 1; and

Figure 3 is a sectional view on the line IIIIII of Figure 2.

My method of treating the ingots comprises placing a hot top on a big-end-down mold, pouring the hot metal into the mold, stripping the mold from the ingot while retaining the hot top in place on the ingot, permitting the ingot to stand with the hot top in place until the ingot has substantially solidified, and finally removing the hot top before charging into the soaking pit. The hot top used is preferably a sectional coke hot top as disclosed in the drawings.

Referring more particularly to the drawings, reference numeral 2 represents the top of 2. rectangular big-end-down mold. The hot top consists of two side slabs 4 and two end slabs 6 between -the ends of theside slabs and the mold. The side slabs have their lower edges bevelled at 8, the outside faces of the bevelled portion being of the same contour as the interior of the mold, the remaining portion of the outside and the entire interior surfaces being fiat. The bottom of the side slabs are substantially wider than the top in order to form a wedge surface on each end of the slab. Slots I!) are provided in the side slabs 4 for the insertion of support hooks l2 which are preformed with a'hook portion l4 having a slightly smaller angle than the slot so that when inserted as shown, the hooks will remainrigidly attached to the slab. The hooks are supported on top of the mold as shown, and the outer portion of each hook is flared at l6 to permit ready placing thereof over the top of the mold. Clearthe moldtoallhw'fonscrap or roughedges theree.

on. By locating slots l below the centers of the slabs, the weight of the overhanging top portion.

causes the bevelled lower portion to contact the mold closely. Further, the support hook wire has ample clearance and causes no separation between mold and hot top, as .it.would .ifthe hook.

were placed under the bottom of the slab. The

.end slabs 6 have a bevelled lower edge l8 similar to the bevelled lower edge 8'; but the tops and bottoms of these slabs are of substantially the same width, slightly lesssthan' the width of the mold, and no wedge surface is formed on the edges.v

In. assembling; the'hot 'top on the mold, apair of hooks l2 are placed in theopenings ID of each side slab 4 andthe slabs placed in position .and supported. from the top of the mold; as shown, with their lower bevelled faces in contact with the .mold. Theend slabs 6 arethen wedged. in place with their outer lower faces in contact with the 'moldwall and their. inner flat faces in contact with the wedge end surfaces of the side slabs 4; This looks the hot top in place and prevents it from floating as the metal rises therein. The joints remain closed during pouring without binding wire or other fastening, because the outward pressure of the steel against thelower part of the slabs is greater. than its outward pressure against thetop of the slabs. The bevelled lower edges contact the mold for a sufiicient distance topreventmetal rising between'the mold and the slabs.

In order to insure thatthe slabs remainonthe ingot after the .mold is. stripped therefrom, the slabsmay be provided'with openings?!) .in their inner surfaces into which the hot metal flows, although we have found that the slabs will generally remain on the ingots without these slots. During stripping the wire hooks [2 are bent upwardly by the mold without pulling the slabs from the ingot.

While the hot top described above is particularly adapted for performing. my method, other types oi;hotitop s"may also be :used as long as they are..easily ,removed from the ingotprior to charging ,into the soakingpit. The slabs .are preferably made ofJcoke orlimestone, since these materials do not stick to the-moldinthe same manner as fireclay: Also, these materials are less harmful to. soaking, pit bottoms andLless likely-,to damage the roll or ingot surfaces during rolling; However, clay, hot. tops While not as satisfactoryas coke .or limestone, maybe'used if' their inside surfaces 1 are coated with a suitable material for preventingstickingof the clay, to the metal. The hot top shown may be easily removed. by the soaking p it. .crane lifting tongs, especiallyif .madepfcokeionlimestone;

In. summary .then,.my,method;'consists .ofi

.(1) Placing, a. hot .top-gona .bigeenddown mold;

(2) .Pouringthehot metal into .the .mold

(3.). Stripping themoldfrom. the ingotarelatively short time aftenpouring. Thelength of time the mold mustremain on the .ingot willIvary with. the ,size of v the ingot, vbut :in most instances, the ingot will. have solidified sufiicientlyto enable the.-mold to be .removed. after 1 a; period .:.of .lfrom 15.to:45 minutes;;

- (4). Permitting-.the ingot .to stand-.ivvithithehot top gin place. untilthe' ingot has substantially solidified; and:

(5) Removing the, hot .top from the ingot .be- .fore;.-charging.;it intoethe -seakinggpits My, improved...method.. permits stripping the molds much sooner after .pouring thanxat present, thus resulting in longer mold life, fewer molds required because of more frequent use of the molds, and quicker delivery of the ingots to the soaking "pit. The reheating time of the ingots is also reducedand a clean ingot is delivered totherollingmill. Further, my method does not involve the -use-of any additional equipment and the flow of the ingot from the pouring floor tothe soaking pit is essentially the same as in usual practice.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modificationsrnay be made without departing .from the scope of. the following claims.

I claim:

1. A- method of treating big-end-down ingots which comprises placing a hot' top on a mold, pouring hot metal into the mold, completely stripping the mold from the ingot between approximately 15 and 45 minutes after pouring while retaining the hot top in place on the ingot, permitting the ingot tostand with the hot top in place until the ingot has substantially solidified, removing the hot top and then chargingthe ingot into the soaking pit.-

2. A method of treating big-end-down ingots which com-prises'placing a sectional hot .top on a mold, pouring'hot metal into'the mold, completely stripping the mold from the ingot between approximately 15 and 45 minutes after pouring while retaining the'hottop in place on the ingot; permitting the ingot to stand with the hot top in place until the ingot has substantially solidified, removing the hot top and then charging the ingot into the soaking pit.

3. A method of treating big-end-down' ingots which comprises placing'a coke hot top on a mold; pouring hot metal into themold, completely stripping the mold from the ingot'between approximately 15' and 45 minutesafter pouring while retaining th'e-hot-top in place on the in got. permitting the ingot to stand with the hot top in place until the ingot has-substantially so"- lidified, removing the hot'top and then charging the ingot into the soaking pit..

4. A. method of'treating big-end-downtingots which comprises placing'a sectional coke hot top on a mold, pouring hot metal into the mold, completelystripping the mold from the ingot be tween approximately "15 and 45'minutes after pouring while retaining thehot'top'inplace'on the ingot, permittingtheingot to stand with the hot topin'place until the ingot 'has substantially solidified, removing the hot top'andthen charging the ingot into .the soaking pit...

EDGAR," MARBURGI REFERENCES CITED.

The-following references" are of :recordin the file of this patent:

UNITEDSTATES PATENTS Number Name Date 1,137,144. Kenney- -Apr. 27,1915 1,737,665 Messier ..Dec.x3; 1929 1,978,996' Gathmann Oct. 30,1934 2,075,039. Kaufiman -Mar. 30,' l93'] 2302,258. Dornin .Dec. 14, 1937 2,433,775 Marburg' .Dec. 30, 1947 2,444,838 Marb'urg, .July, .6,' 1948 

